1. Field of the Invention
The present invention relates to a rotary apparatus usable as a driver in a rotary mechanism used in a light deflector of an image forming apparatus in a digital copying machine, a laser beam printer, or the like, and a deflection-scanning apparatus using the rotary apparatus.
2. Related Background Art
FIG. 1 is a view illustrating the overall structure of a scanning optical system with a deflection-scanning apparatus. As illustrated in FIG. 1, a laser unit 2 is mounted in an optical box 1, a rotary polygonal mirror 3 of the deflection-scanning apparatus and lenses 4 and 5 are arranged along an optical path L emerging from the laser unit 2 in the optical box 1, and a photosensitive member 6 of a recording medium is disposed outside of the optical box 1.
Laser light emerging from the laser unit 2 is deflected by the rotary polygonal mirror 3 rotatably supported by a bearing apparatus, transmitted through the lenses 4 and 5 and projected as a light spot on the photosensitive member 6 disposed outside of the optical box 1. A main scan is thus performed.
In the vicinity of the photosensitive member 6, there are arranged a corona discharger for uniformly electrifying a surface of the photosensitive member 6, a developing unit for visualizing an electrostatic latent image formed on the surface of the photosensitive member 6 to obtain a toner image, a transferor for transferring the toner image to a recording paper, and the like. Recording information of the laser light generated by the laser unit 2 is thus printed on the recording paper or the like.
For example, in a deflection-scanning apparatus as illustrated in FIG. 2 which is disclosed in Japanese Patent Application Laid-Open No. 6-123850, a rotary polygonal mirror 3 is supported rotatably about a fixed shaft 31 through a flange 27 and is rotatable at a high speed by means of a magnetic action between a permanent magnet 30 on a rotor side and a yoke 32 with an electromagnetic coil 33 on a stator side opposed to the rotor side.
However, since the yoke 32 is supported in a cantilever manner, vibrations occur due to the rotation of the rotor caused by a change of poles. The vibration adversely influences a life of the rotary apparatus and a deflection precision of the beam deflected by the deflection-scanning apparatus.